Considerable evidence indicates that in the Western world toxigenic diarrhea produced by Escherichia coli infection may be a very common and frequently disabling disorder in adults and children. The general objectives of this proposal are to purify the enterotoxin of Escherichia coli and to study the immunological, chemical and toxigenic properties of the toxin with the aim of utilizing such knowledge for the development of rational and effective therapeutic measures for diarrheal disorders associated with these and other toxigenic agents. The activity of the toxin will be detected by a very sensitive assay which involves the inhibition of epidermal growth factor stimulated DNA synthesis in human fibroblasts in tissue culture. The enterotoxin from E. coli culture filtrates will be purified by affinity chromatography on specific adsorbent columns consisting of a) ganglioside-agarose, b) agarose derivatives of cholera toxin antibodies, and c) agarose derivatives of E. coli enterotoxin antibodies. The properties of the purified toxin will be studied, and soluble ganglioside-polymers will be synthesized as potential therapeutic agents in preventing and reversing the action of the enterotoxins. Drugs which may reverse the stimulation of adenylate cyclase by the toxin will be sought, and means of preparing special immunogens as potentially useful agents for effective vaccination procedures will be studied.